1. Field of the Invention
The present invention relates to a slicing machine and a slicing method by use of the slicing machine and, in particular, to such slicing machine and method in which a semiconductor ingot is sliced out into thin pieces to manufacture semiconductor wafers.
2. Description of the Related Art
In a slicing machine, an inner peripheral cutting edge blade or an outer peripheral cutting edge blade is rotated at a high speed and the rotating blade is then pressed against a semiconductor ingot to thereby manufacture semiconductor wafers. In this case, from the viewpoint of the yield rate of the semiconductor wafers and post treatment operation thereof, it is advantageous to minimize the displacements of the blade during cutting as much as possible to thereby reduce the degree of curving of the wafers.
However, recently, a semiconductor wafer having an increased diameter has been demanded, requiring a blade having an increased diameter. Due to the increased diameter of the blade, the cutting position of the blade during the cutting operation thereof may be varied, causing the wafer surface to be curved. In addition to this, the surface of the wafer sliced may be curved due to the uneven shapes of the cutting edge, clogging in the cutting edge, the surface tension of a grinding solution, the variable cutting resistances and the like.
Under these circumstances, conventionally, there have been proposed various measures to prevent curving of the wafer caused by the cutting operation of the rotating blade.
For example, in Publication of Japanese Patent Application Laid-open (Tokkai) No. 61-98513, there are provided air nozzles on both sides of the surface of a blade and there are disposed blade sensors respectively adjacent to the air nozzles. The position of the blade, in which the blade is in a non-loaded state, is set as a zero position. If the blade sensor detects the amount of displacement of the blade from the zero position and the direction of displacement thereof, then air is injected from the air nozzle to thereby correct and thus eliminate the displacement.
Also, in Publication of Japanese Patent Application Laid-open (Tokkai) No. 62-225308, there are provided cooling/lubricating water supply nozzles on both sides of the surface of a blade and there are disposed blade sensors respectively adjacent to the nozzles. If any displacement of the blade is detected, then in a similar manner to the above-mentioned Publication of Japanese Patent Application Laid-open (Tokkai) No. 61-98513, cooling/lubricating water is injected out to the blade to thereby correct the displacement of the blade.
Further, in Publication of Japanese Patent Application Laid-open (Tokkai) No. 1-110105, there are provided negative pressure suction type nozzles on both sides of the surface of a blade and there are disposed blade sensors respectively adjacent to the nozzles. In this arrangement, if the blade sensor detects the displacement of the blade, then air is blown out from the negative pressure suction nozzle disposed opposed to the direction of the displacement of the blade to produce a negative pressure to thereby correct the displacement of the blade.
In addition, in Publication of Japanese Utility Model Application Laid-open (Jikkai) No. 61-122811, an ingot or a blade is arranged such that it can be moved in the axial direction thereof, and there is provided a blade sensor which is used to detect the axial displacement of the blade. In this arrangement, if any displacement of the blade is detected in accordance with a signal from the blade sensor, then the ingot or blade is moved in the axial direction thereof to thereby correct the axial displacement of the blade.
As described above, in the above conventional slicing methods by use of a slicing machine, the position of the blade before cutting is set as the zero position and, by detecting any displacement (or curving) in a plus direction or in a minus direction from the zero position by use of the blade sensor, the nozzle or the like is used to return the displacement to the zero position to thereby correct the displacement of the blade.
However, the inner peripheral cutting edge blade exerts its tension by extending up the outer peripheries and thus the portions of the blade around the inner peripheral cutting edge are weaker in rigidity than the outer peripheries of the blade. For this reason, when sliced in a weaker rigidity state, the wafer sliced is easy to curve and the curving cannot be corrected sufficiently because of the weak rigidity, with the result that it is hard to obtain a working accuracy necessary for the wafer.